title: Mutations in the parainfluenza virus 5 fusion protein reveal domains important for fusion triggering and metastability.
abstract: Paramyxovirus membrane glycoproteins F (fusion protein) and HN, H, or G (attachment protein) are critical for virus entry, which occurs through fusion of viral and cellular envelopes. The F protein folds into a homotrimeric, metastable prefusion form that can be triggered by the attachment protein to undergo a series of structural rearrangements, ultimately folding into a stable postfusion form. In paramyxovirus-infected cells, the F protein is activated in the Golgi apparatus by cleavage adjacent to a hydrophobic fusion peptide that inserts into the target membrane, eventually bringing the membranes together by F refolding. However, it is not clear how the attachment protein, known as HN in parainfluenza virus 5 (PIV5), interacts with F and triggers F to initiate fusion. To understand the roles of various F protein domains in fusion triggering and metastability, single point mutations were introduced into the PIV5 F protein. By extensive study of F protein cleavage activation, surface expression, and energetics of fusion triggering, we found a role for an immunoglobulin-like (Ig-like) domain, where multiple hydrophobic residues on the PIV5 F protein may mediate F-HN interactions. Additionally, destabilizing mutations of PIV5 F that resulted in HN trigger-independent mutant F proteins were identified in a region along the border of F trimer subunits. The positions of the potential HN-interacting region and the region important for F stability in the lower part of the PIV5 F prefusion structure provide clues to the receptor-binding initiated, HN-mediated F trigger.
authors.affiliation: Department of Molecular Biosciences.
authors.forename: Sayantan
authors.initials: S
authors.lastname: Bose
authors.forename: Carissa M
authors.initials: CM
authors.lastname: Heath
authors.forename: Priya A
authors.initials: PA
authors.lastname: Shah
authors.forename: Maher
authors.initials: M
authors.lastname: Alayyoubi
authors.forename: Theodore S
authors.initials: TS
authors.lastname: Jardetzky
authors.forename: Robert A
authors.initials: RA
authors.lastname: Lamb
mesh_terms: D000818:Animals; D002460:Cell Line; D015707:HN Protein / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D006801:Humans; D009154:Mutation; D045402:Parainfluenza Virus 5 / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D011485:Protein Binding; D055550:Protein Stability; D017434:Protein Structure, Tertiary; D019351:Rubulavirus Infections / Q000821:virology*; D014760:Viral Fusion Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D053586:Virus Internalization
chemical_list: D015707:HN Protein; D014760:Viral Fusion Proteins